1. Field of the Invention
The present invention relates to the field of semiconductor processing and more specifically to a method and apparatus for smoothing and adding silicon to a silicon or silicon alloy surface.
2. Discussion of Related Art
Semiconductor devices such as microprocessors and memories are fabricated by various steps including the deposition and removal of silicon films. Silicon deposition and removal steps as well as other process steps can cause the surface of silicon films to become rough and contaminated. Rough and contaminated silicon surfaces can generally lead to poor quality interfaces, which can lead to poor device performance and reliability. It would therefore be desirable to be able to accurately, reliably, and uniformly treat a silicon surface in order to remove any surface contaminants contained therein and to provide a smooth silicon surface finish. It would also be desirable to be able to treat a silicon surface in a chamber, which could subsequently be used to deposit a silicon film. In this way after removing the surface contaminants and smoothing the silicon surface one could directly deposit a silicon film onto the uncontaminated smooth silicon surface without exposing the treated surface to an oxidizing or contaminating environment.
A method and apparatus for treating a silicon surface is disclosed. As part of the method and apparatus, a substrate having a silicon or silicon alloy surface can be placed into a process chamber and heated to a temperature of approximately between 700xc2x0-1300xc2x0 C. While the substrate is heated, the silicon surface can be exposed to a combination of process gasses, where the process gasses can include a first gas mixture of a silicon etchant mixed with a silicon source gas and disposed in a carrier gas. The first gas mixture can flow into the process chamber at one or more locations. A second gas mixture may flow into the process chamber at one or more locations that are different from the locations for the first gas mixture. The second gas mixture may use the same etchant, silicon source gas, and carrier gas as the first gas mixture but may be applied at different concentrations and/or flow rates into the process chamber. The etchant can be, for example, HCl, the silicone source gas can be, for example, silane gas, and the carrier gas can be for example, hydrogen gas. The first gas mixture and the second gas mixture can be pre-mixed. The first and second gas mixtures can flow through two or more separate channels into the process chamber to be applied onto a spinning wafer. As a result of the channels, the process gases can be applied onto the silicon surface where the first gas mixture can flow to a first area over the wafer that is different from a second area over the wafer where the second gas mixture flows. The process can provide for uniform smoothing of an exposed silicon surface and the process can provide for silicon to be uniformly added to the silicon surface.